Counter-doped LDMOS drift regions for breakdown voltage
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Solution Overview
Problem
Conventional LDMOS transistors have a low breakdown voltage, which is impaired as the voltage applied to the gate electrode increases, leading to accelerated impact ionization and reduced performance.
Innovation Solution
The introduction of counter-doped regions in the drift region, aligned vertically to the semiconductor substrate, which divide the drift region into parts and reduce impact ionization by diverging electric current, thereby increasing the breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If voltage applied to the gate electrode is increased to improve transistor performance, then gain and power output are improved, but breakdown voltage decreases due to accelerated impact ionization
Solution Approach 1:
The drift region is divided into multiple segments by introducing counter-doped regions, which create multiple smaller drift regions separated by oppositely doped regions. This segmentation reduces the electric field strength in each segment, thereby reducing impact ionization and preventing premature breakdown while allowing higher overall voltage operation for improved power output
Solution Approach 2:
Counter-doped regions are introduced at specific locations within the drift region to create local areas with opposite doping polarity. These localized regions modify the electric field distribution specifically where needed, reducing impact ionization in high-field areas while maintaining the overall high-voltage blocking capability and power output of the device
2Ease of manufacture
If conventional LDMOS transistor structure is used, then manufacturing is simple and cost-effective, but breakdown voltage is low limiting performance
Solution Approach 1:
Counter-doped regions are formed during the manufacturing process using preliminary ion implantation or in-situ doping techniques, integrating the breakdown voltage enhancement into the existing fabrication flow. This preliminary action allows the improved structure to be created without adding significant manufacturing complexity or cost
Solution Approach 2:
The doping concentration and depth parameters are optimized to achieve the desired breakdown voltage improvement. By carefully controlling the doping parameters during manufacturing, the counter-doped regions are created with precise characteristics that enhance reliability while maintaining ease of manufacture through standard process adjustments
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively increases the breakdown voltage of LDMOS transistors by reducing impact ionization through the use of counter-doped regions, enhancing their performance and reliability.
Implementation Method 1
the breakdown voltage of the LDMOS transistor can be improved... reduce impact ionization by diverging electric current
Data Source
AI summary
The present disclosure provides a method for forming a semiconductor device, including: providing a semiconductor substrate; forming a well region and a drift region in the semiconductor substrate; and forming one or more counter-doped regions in the drift region, the one or more counter-doped regions being aligned along a direction vertical to the semiconductor substrate to divide the drift region into a plurality of parts. The semiconductor fabrication method also includes: forming a gate structure on the semiconductor substrate, the gate structure covering a portion of the well region and a portion of the drift region; and forming a source electrode in the well region on one side of the gate structure and a drain electrode in the drift region on another side of the gate structure.